This invention relates to a safety restraint system for an occupant of an adjustable seat in a vehicle, and more particularly to an electromechanical coupling of a seat belt retractor having a tension-eliminating mechanism including an electrically operated actuator with a seat adjuster mechanism.
Developed recently as a component of a safety restraint system to protect a vehicle seat occupant during emergency conditions such as in a collision or sudden deceleration is a seat belt retractor of the so-called tensionless type. In a retractor of this type, a reel for winding a seat belt webbing is carried by a shaft which is constantly spring-biased in the direction to retract the webbing, so that the seat belt can be brought into a properly restraining state merely by pulling out a needful length of the webbing from the retractor to couple a tongue attached to the free end of the webbing to a buckle attached to a separately supported webbing of a short and definite length, or by closing a door in the case of a so-called passive safety belt. Since the exertion of a constant tension on the seat belt in this state causes considerable discomfort and inconvenience to the seat occupant, the retractor has a tension-eliminating mechanism which is a one-way locking mechanism to inhibit the reel from turning in the retracting direction by energization of an electrically operated actuator in response to closing of a buckle switch, or a door switch in the case of a passive seat belt, to force a detent to engage a ratchet. Even in this state the webbing can be protracted from the retractor according as the occupant changes his posture within the seat. In addition, the retractor has an emergency locking mechanism including a deceleration-responsive device the function of which results in engagement of another detent with another ratchet to inhibit the reel from turning in the belt-protracting direction.
The tension-eliminating function of this retractor is quite favorable for the comfort of the seat occupant, but it causes considerable inconvenience when this retractor is applied to an adjustable seat which is prevailing in the current cars. The occupant of such a seat often intends to change the position of the seat or the inclination of the seatback after wearing of the seat belt, but the accomplishment of the intention is inevitably accompanied by a change in the positional relation between the occupant and the seat belt maintained in the tensionless state, meaning a deviation of the seat belt from a properly restraining state. A serious problem arises particularly when the seat is moved rearward or the seatback is tilted backward because such a way of seat adjustment causes an increase in the amount of slack of the tensionless seat belt with respect to the changed position or posture of the seat occupant, so that the seat belt might become ineffective in restraining the occupant during an emergency. Therefore, it becomes necessary to unfasten the seat belt at each time of seat adjustment to allow the retractor to resume the retracting state and refastening the seat belt after completion of seat adjustment to thereby render the seat belt tensionless in a properly restraining state.